Preparation and Characterization of porous tubular scaffold made of PCL/PLCL blends for vascular tissue engineering / Azizah Pangesty and Mitsugu Todo

Porous tubular scaffolds had been developed by physically blending poly-ε-caprolactone (PCL) and poly-(lactide-co-ε-caprolactone) (PLCL) using solid-liquid phase separation method subsequent with freeze-drying method. The effect of blending ratio on the morphology and mechanical properties of PCL/PLCL blends tubular scaffold had been investigated. The blending were confirmed using infrared spectroscopy. The microstructure behaviour were observed using scanning electron microscopy and the mechanical properties were evaluated using ring tensile test. It was concluded that the resulted tubular scaffold possessed an improved elastic modulus and enlarged pore size as the content of PLCL increased. The tubular scaffold containing 75% PLCL was found as the optimum blends ratio in terms of elastic modulus and rebound properties. The tubular scaffold made of PCL/PLCL blends has a potential for vascular tissue engineering application

Biomechanical alteration of stress and strain distribution associated with vertebral fracture

The phenomenon of recurrent fractures at the adjacent level of a fractured vertebra is becoming a major concern amongst medical practitioners. To date, the underlying cause of this phenomenon is still elusive; therefore, a further investigation is in dire need in order to achieve satisfactory clinical outcomes in the future. In the present study, an image based finite element analysis (FEA) was used to investigate the biomechanical alterations of spine that have been diagnosed with first lumbar (L1) vertebral compression fracture as compared to a healthy spine. The FEA assessment was made based on the model’s stress and strain distributions. A complimentary examination of bone density distribution and kyphotic deformity angle of the model would give further details on the underlying cause of this phenomenon. The results showed that the vertebral fracture model tends to produce higher stresses and strains generation in comparison to the healthy vertebral model, especially at the adjacent level of the fractured vertebra. These conditions were highly correlated to the bad quality of the bone strength due to osteoporosis, and the kyphotic structural of the fractured vertebral model. The combination of these two elements has put the structural integrity of the vertebrae at the stake of bone fracturing even under the influence of daily living activity

Engineered chitosan for improved 3D tissue growth through Paxillin-FAK-ERK activation

Scaffold engineering has attracted significant attention for three-dimensional (3D) growth, proliferation and differentiation of stem cells in vitro. Currently available scaffolds suffer from issues such as poor ability for cell adhesion, migration and proliferation. This paper addresses these issues with 3D porous chitosan scaffold, fabricated and functionalized with cysteine-terminated Arg-Gly-Asp (Cys-RGD) tri-peptide on their walls. The study reveals that the compressive moduli of the scaffold is independent to RGD functionalization but shows dependence on the applied freezing temperature (TM) during the fabrication process. The low freezing TM (−80°C) produces scaffold with high compressive moduli (14.64 ± 1.38 kPa) and high TM (−30°C) produces scaffold with low compressive moduli (5.6 ± 0.38 kPa). The Cys-RGD functionalized scaffolds lead to significant improvements in adhesion (150%) and proliferation (300%) of human mesenchymal stem cell (hMSC). The RGD-integrin coupling activates the focal adhesion signaling (Paxillin-FAK-ERK) pathways, as confirmed by the expression of p-Paxillin, p-FAK and p-ERK protein, and results in the observed improvement of cell adhesion and proliferation. The proliferation of hMSC on RGD functionalized surface was evaluated with scanning electron microscopy imaging and distribution though pore was confirmed by histochemistry of transversely sectioned scaffold. The hMSC adhesion and proliferation in scaffold with high compressive moduli showed a constant enhancement (with a slope value 9.97) of compressive strength throughout the experimental period of 28 days. The improved cell adhesion and proliferation with RGD functionalized chitosan scaffold, together with their mechanical stability, will enable new interesting avenues for 3D cell growth and differentiation in numerous applications including regenerative tissue implants

Biomechanical Alteration of Stress and Strain Distribution Associated with Vertebral Fracture / Muhammad Hazli Mazlan...[et al.]

The phenomenon of recurrent fractures at the adjacent level of a fractured vertebra is becoming a major concern amongst medical practitioners. To date, the underlying cause of this phenomenon is still elusive; therefore, a further investigation is in dire need in order to achieve satisfactory clinical outcomes in the future. In the present study, an image based finite element analysis (FEA) was used to investigate the biomechanical alterations of spine that have been diagnosed with first lumbar (L1) vertebral compression fracture as compared to a healthy spine. The FEA assessment was made based on the model’s stress and strain distributions. A complimentary examination of bone density distribution and kyphotic deformity angle of the model would give further details on the underlying cause of this phenomenon. The results showed that the vertebral fracture model tends to produce higher stresses and strains generation in comparison to the healthy vertebral model, especially at the adjacent level of the fractured vertebra. These conditions were highly correlated to the bad quality of the bone strength due to osteoporosis, and the kyphotic structural of the fractured vertebral model. The combination of these two elements has put the structural integrity of the vertebrae at the stake of bone fracturing even under the influence of daily living activity

Dynamic Finite Element Analysis of Mobile Bearing Type Knee Prosthesis under Deep Flexional Motion

The primary objective of this study is to distinguish between mobile bearing and fixed bearing posterior stabilized knee prostheses in the mechanics performance using the finite element simulation. Quantifying the relative mechanics attributes and survivorship between the mobile bearing and the fixed bearing prosthesis remains in investigation among researchers. In the present study, 3-dimensional computational model of a clinically used mobile bearing PS type knee prosthesis was utilized to develop a finite element and dynamic simulation model. Combination of displacement and force driven knee motion was adapted to simulate a flexion motion from 0° to 135° with neutral, 10°, and 20° internal tibial rotation to represent deep knee bending. Introduction of the secondary moving articulation in the mobile bearing knee prosthesis has been found to maintain relatively low shear stress during deep knee motion with tibial rotation

Excellency of Hydroxyapatite Composite Scaffolds for Bone Tissue Engineering

The hydroxyapatite [HAp, Ca10(PO4)6(OH)2] has a variety of applications in bone fillers and replacements due to its excellent bioactivity and osteoconductivity. It comprises the main inorganic component of hard tissues. Among the various approaches, a composite approach using several components like biopolymer, gelatin, collagen, and chitosan in the functionalization of scaffolds with HAp has the prospective to be an engineered biomaterial for bone tissue engineering. HAp composite scaffolds have been developed to obtain a material with different functionalities such as surface reactivity, bioactivity, mechanical strength, and capability of drug or growth factor delivery. Several techniques and processes for the synthesis and fabrication of biocompatible HAp composite scaffolds suitable for bone regeneration are addressed here. Further, this chapter described the excellences of various HAp composite scaffolds used in in vitro and in vivo experiments in bone tissue engineering

Biomechanical evaluation of two different types of interbody cages in posterior lumbar interbody fusion

Posterior lumbar interbody fusion (PLIF) related complications such as cage instability, cage subsidence and pedicle screws loosening are among the most prevalent cases reported postoperatively. These conditions are highly related to mechanical factors (PLIF design and material), patient health condition as well as activities conducted by the patient after undergone the surgery. Latest advancement on PLIF technology has created a new technique that allows the application of unilateral cage insertion in an oblique orientation. This solution has potentially overcome the problem related to an unintended mechanical and clinical shortcoming, provided that a bilateral posterior instrumentation (PI) is instrumented to the construct and the cage is fabricated from a material that is closely imitate the modulus elasticity of the cortical bone. In order to prove these statements, an image based finite element analysis (FEA) was conducted to assess the phenomena of cage subsidence and screw loosening by examining the stress profile on the cage construct and the vertebral bodies. Obliquely-placed unilateral PLIF with PI showed the most promising results. It showed the most minimal stress distortion at cage-endplate and pedicle screw-bone interface. In conclusion, the selection of a biocompatible cage material is the most crucial factors that has to be considered in achieving biomechanical superiority in PLIF surgery

Development and Characterization of Gear Shape Porous Scaffolds Using 3D Printing Technology

Continuous porous structures of biodegradable polylactic acid (PLA) were fabricated using a rapid prototyping machine with the three dimensional fused deposition modeling (FDM) technique. Effects of two different circle packing methods, the square (SQ) and the hexagonal (HEX) packings, and different pore diameters on the compressive mechanical properties were examined. The compression test results showed that SQ1 and HEX1 with 1 mm pore diameter had the largest compressive properties, suggesting that the microstructures were well constructed compared to the other specimens. Although SQ0.7 and HEX0.7 exhibited the lowest porosities, the modulus values were lowest, indicating that the microvoids degraded the stiffness of the structures. Scanning electron microscopy of the damaged regions suggested that microcracks were generated along the interlayers or within the layers due to bending deformation and the final fracture were initiated with these microcracking mechanism. It is thus concluded that the fabrication process must be improved so that the microcrack formation is minimized. Finite element analysis was used as an evaluation tools by comparing the experimental compressive modulus and a good agreement was exhibited correspondingly